In the treatment of oil, gas and geothermal wells and/or subterranean formations penetrated by wells, it is important that well treatment agents be delivered into defined targeted areas. Well fluids are generally complex mixtures of aliphatic hydrocarbons, aromatics, hetero-atomic molecules, anionic and cationic salts, acids, sands, silts, clays and a vast array of other components. The nature of these fluids, combined with the severe conditions of heat, pressure, and turbulence to which they are often subjected, are contributory factors to the formation and deposition of contaminants, such as scales, salts, paraffins, corrosion, bacteria and asphaltenes in production wells.
A common site for the formation and deposition of such contaminants in oil or gas wells is the annular space between the production tubing and casing. The annulus may be a static area or may produce gas or liquid. The formation and deposition of such contaminants may reduce well productivity. Further, the presence of contaminants, such as scales, in the annulus may make it difficult or impossible to remove the tubing for servicing.
In addition, such contaminants form in other equipment and flow conduits used in the production of oil, gas and other fluids. Acute problems result when such contaminants develop in equipment and flow conduits used in gas and oil production, refineries and other fluid processing facilities.
Well treatment agents are known in the art for inhibiting or controlling such unwanted contaminants. In some instances, it is necessary for well treatment agents to be released into their targeted area over a sustained period of time. For instance, it is typically desired that well treatment agents which inhibit the formation or deposition of contaminants such as scales, salts, paraffins, corrosion, bacteria and asphaltenes be slowly released in production wells, subterranean formations, equipment and flow conduits used in gas production and oil production. The formation and deposition of such unwanted contaminants decrease permeability of the formation and reduce well productivity and can completely block the well tubular in severe cases.
U.S. Pat. No. 7,491,682 and U.S. Pat. No. 7,493,955, both of which are herein incorporated by reference, disclose the use of composites for the slow release of well treatment agents. U.S. Pat. No. 7,475,730 and U.S. Patent Publication No. 20090114247, both of which also herein incorporated by reference, further disclose a method of inhibiting and/or removing unwanted contaminants from wells, flow conduits and vessels with a foamed treatment composition.
In well service operations, such as drilling operations, hydraulic fracturing operations and completion operations, it is often important that the activity of the well treatment agent be delayed for some time after being introduced into the well and/or subterranean producing formation. For example, in hydraulic fracturing, the viscosity of the fracturing fluid is typically decreased after placement of proppant into the fracture in order that the fluid may flow naturally from the formation. While breakers are typically incorporated into the fracturing fluid, their activity is most desirably delayed until after the proppant is placed into the fracture. Further, it is often desirable to delay crosslinking in a fracturing fluid until after the fluid has traveled to a designated distance into the wellbore and/or through the formation. At that point, gelling of the fluid is desired.
Breakers are also used to break down filter cakes which are formed during wellbore operations. For instance, breakers are often included in the drilling fluid to break down filter cakes. It is desirable, however, that the breaker not be functional until break down of the filter cake is needed.
While composites have been successful in the slow release of well treatment agents in drilling, stimulation and completion operations, methods of improving the slow or delayed release of well treatment agents, especially liquid well treatment agents, as well as improved methods for delivering such treatment agents into wells, formations, conduits and/or vessels have been sought. In particular, alternatives have been sought for delivering well treatment agents into targeted areas such that the well treatment agent may be slowly released and the activity of the treatment agent may be delayed.